Quantitative structure determination of adsorbed formate and surface hydroxyls on Fe3O4(001)

Using the chemically specific techniques of normal incidence X-ray standing waves and photoelectron diffraction, we have investigated the dissociative adsorption of formic acid on the Fe₃O₄(001) surface, specifically probing the local structures of both the adsorbed formate and resulting surface hydroxyl. Using model independent direct methods, we reinforce the observations of a previous surface X-ray diffraction study that the formate molecule adsorbs with both oxygens atop octahedrally coordinated surface Fe cations and that ∼60% of the formate is adsorbed in the so called tet site. We additionally determine, for the first time, that the surface hydroxyl species are found at the so called int site. This confirms previous DFT predictions and reinforces the pivotal role the surface hydroxyl plays in lifting the subsurface cation vacancy termination of the Fe₃O₄(001) surface.

Stabilisation of tri-valent ions with a vacant coordination site at a corrole-metal interface

By exploiting an established on-surface metallation strategy, we address the ability of the corrolic macrocycle to stabilise transition metal ions in high-valent (III) oxidation states in metal-supported molecular layers. This approach offers a route to engineer adsorbed metal complexes that cannot be easily fabricated by organic synthesis methods and bear a vacant axial coordination site for catalytic conversions.

Validation of the inverted adsorption structure for free-base tetraphenyl porphyrin on Cu(111)

Utilising normal incidence X-ray standing waves we rigourously scrutinise the "inverted model" as the adsorption structure of free-base tetraphenyl porphyrin on Cu(111). We demonstrate that the iminic N atoms are anchored at near-bridge adsorption sites on the surface displaced laterally by 1.1 ± 0.2 Å in excellent agreement with previously published calculations.

Local adsorption structure and bonding of porphine on Cu(111) before and after self-metalation

We have experimentally determined the lateral registry and geometric structure of free-base porphine (2H-P) and copper-metalated porphine (Cu-P) adsorbed on Cu(111), by means of energy-scanned photoelectron diffraction (PhD), and compared the experimental results to density functional theory (DFT) calculations that included van der Waals corrections within the Tkatchenko-Scheffler approach. Both 2H-P and Cu-P adsorb with their center above a surface bridge site. Consistency is obtained between the experimental and DFT-predicted structural models, with a characteristic change in the corrugation of the four N atoms of the molecule's macrocycle following metalation. Interestingly, comparison with previously published data for cobalt porphine adsorbed on the same surface evidences a distinct increase in the average height of the N atoms above the surface through the series 2H-P, Cu-P, and cobalt porphine. Such an increase strikingly anti-correlates the DFT-predicted adsorption strength, with 2H-P having the smallest adsorption height despite the weakest calculated adsorption energy. In addition, our findings suggest that for these macrocyclic compounds, substrate-to-molecule charge transfer and adsorption strength may not be univocally correlated.

Probing the interplay between geometric and electronic structure in a two-dimensional K-TCNQ charge transfer network

Scanning tunnelling microscopy (STM), low energy electron diffraction (LEED), ultraviolet and soft X-ray photoelectron spectroscopy (UPS and SXPS) have been used to characterise the formation of a coadsorption phase of TCNQ and K on Ag(111), while the normal incident X-ray standing waves (NIXSW) technique has been used to obtain quantitative structural information. STM and LEED show that an ordered incommensurate phase is formed in which the K atoms are surrounded by four TCNQ molecules in a 'windmill' motif, characteristic of other metal/TCNQ phases, in which the nominal TCNQ : K stoichiometry is 1 : 1. UPS and SXPS data indicate the TCNQ is in a negatively-charged state. NIXSW results show that the carbon core of the TCNQ is essentially planar at a height above the Ag(111) surface closely similar to that found without coadsorbed K. In the presence of TCNQ the height of the K ions above the surface is significantly larger than on clean Ag(111), and the ions occupy sites above 'holes' in the TCNQ network. NIXSW data also show that the N atoms in the molecules must occupy sites with at least two different heights above the surface, which can be reconciled by a tilt or twist of the TCNQ molecules, broadly similar to the geometry that occurs in bulk TCNQ/K crystals.

Direct measurement of Ni incorporation into Fe3O4(001)

The normal incidence X-ray standing wave (NIXSW) technique has been used to follow the evolution of the adsorption geometry of Ni adatoms on the Fe₃O₄(001)-(√2 × √2)R45° surface as a function of temperature.

The normal incidence X-ray standing wave (NIXSW) technique has been used to follow the evolution of the adsorption geometry of Ni adatoms on the Fe₃O₄(001)-(√2 × √2)R45° surface as a function of temperature. Two primary surface region sites are identified: a bulk-continuation tetrahedral site and a sub-surface octahedral site, the latter site being preferred at higher annealing temperatures. The ease of incorporation is linked to the presence of subsurface cation vacancies in the (√2 × √2)R45° reconstruction and is consistent with the preference for octahedral coordination observed in the spinel compound NiFe₂O₄.

Soft X-ray Spectroscopy of a Complex Heterojunction in High-Efficiency Thin-Film Photovoltaics: Intermixing and Zn Speciation at the Zn(O,S)/Cu(In,Ga)Se2 Interface

The chemical structure of the Zn(O,S)/Cu(In,Ga)Se₂ interface in high-efficiency photovoltaic devices is investigated using X-ray photoelectron and Auger electron spectroscopy, as well as soft X-ray emission spectroscopy. We find that the Ga/(Ga+In) ratio at the absorber surface does not change with the formation of the Zn(O,S)/Cu(In,Ga)Se₂ interface. Furthermore, we find evidence for Zn in multiple bonding environments, including ZnS, ZnO, Zn(OH)₂, and ZnSe. We also observe dehydrogenation of the Zn(O,S) buffer layer after Ar⁺ ion treatment. Similar to high-efficiency CdS/Cu(In,Ga)Se₂ devices, intermixing occurs at the interface, with diffusion of Se into the buffer, and the formation of S-In and/or S-Ga bonds at or close to the interface.

Characterization of Sulfur Bonding in CdS:O Buffer Layers for CdTe-based Thin-Film Solar Cells

On the basis of a combination of X-ray photoelectron spectroscopy and synchrotron-based X-ray emission spectroscopy, we present a detailed characterization of the chemical structure of CdS:O thin films that can be employed as a substitute for CdS layers in thin-film solar cells. It is possible to analyze the local chemical environment of the probed elements, in particular sulfur, hence allowing insights into the species-specific composition of the films and their surfaces. A detailed quantification of the observed sulfur environments (i.e., sulfide, sulfate, and an intermediate oxide) as a function of oxygen content is presented, allowing a deliberate optimization of CdS:O thin films for their use as alternative buffer layers in thin-film photovoltaic devices.

Face-dependent bond lengths in molecular chemisorption: the formate species on Cu(111) and Cu(110)

Many previous structural studies of molecular adsorbates on metal surfaces indicate that the local coordination and bonding is closely similar to that in organometallic compounds, implying that the metallic substrate has no significant influence. Here we show that such an influence is detectable for one model system, namely, the formate species, HCOO, adsorbed on the atomically rough and smooth (110) and (111) surfaces of Cu, leading to a statistically significant difference (0.09±0.05  Å) in the Cu-O chemisorption bond length. The effect is reproduced in density functional theory calculations.

The structure of furan reaction products on Pd(111)

Previous experimental studies of the interaction of molecular furan, C(4)H(4)O, with Pd(111) have led to the conclusion that partial dissociation leads to two coadsorbed reaction products, CO and a C(3)H(3) species. Using density functional theory (DFT), a range of possible molecular conformation and adsorption sites of the C(3)H(3) species have been explored and the lowest energy structures, and associated C 1s photoelectron core-level binding energy shifts (CLSs), have been determined. Comparison of these CLS values with published experimental measurements allows one possible conformation to be rejected. New simulations of the C 1s scanned-energy mode photoelectron diffraction (PhD) spectra for several of lowest-energy structures found in DFT are compared with the results of an earlier experimental study. The lowest energy structure found in DFT is not consistent with the PhD data, suggesting that energy barriers to achieve the associated conformation cannot be overcome in the dissociation process. Through consideration of the results of both methods, the most probable surface structures are discussed.

Methoxy species on Cu(110): understanding the local structure of a key catalytic reaction intermediate

Partial oxidation of methanol to formaldehyde over Cu(110) is one of the most studied catalytic reactions in surface science, yet the local site of the reaction intermediate, methoxy, remains unknown. Using a combination of experimental scanned-energy mode photoelectron diffraction, and density functional theory, a consistent structural solution is presented in which all methoxy species occupy twofold coordinated "short-bridge" adsorption sites. The results are consistent with previously-published scanning tunnelling microscopy images and theoretical calculations of the reaction mechanism.

Suppression of natural killer cell activity by ethanol consumption and food restriction

Effects of 4-week food restriction and ethanol consumption on natural killer (NK) cell activity and carcass composition were evaluated. Female, C57BL/6 mice given water (H2O) or ethanol (20% w/v, ETOH) ad libitum were placed in one of three dietary groups: unrestricted (UNR), moderately restricted (MR, 2.2 g/day), or severely restricted (SR, 1.8 g/day). Food restriction alone (MR, SR) significantly reduced body, spleen, and thymus weights; carcass lipid content (SR only); spleen cell number; and baseline and interleukin-2 (rIL-2) stimulated NK cell activities. Ethanol consumption was unaffected by food restriction and in restricted mice it did not suppress food intake. Thus, average calories derived from ethanol increased from 30% (UNR) to 40% (SR) with the degree of food restriction in these groups. Mice given ethanol and restricted food intake had at least as heavy or heavier body, spleen, and thymus weights than water-drinking (H2O) counterparts. Spleen cell number was reduced in ethanol-consuming (ETOH), food restricted groups compared with UNR H2O control. Baseline NK cell activity was suppressed 50% to 90% in all ETOH and food-restricted groups. rIL-2 stimulated NK cell activity was suppressed 18% to 76% in food restricted mice independent of ethanol intake. These results indicate that supplementary ethanol calories did not enhance NK cell activity in UNR ETOH mice, nor did they protect splenic NK cell activity from the suppressant effects of food restriction. Ethanol consumption significantly increased carcass lipid content in all groups compared with their H2O counterparts. This increase was largely responsible for the preservation of body weight in ETOH mice especially during food restriction.

Uterine herpes virus infection with multifocal necrotizing endometritis

A case of herpes simplex virus (HSV) infection was diagnosed by biopsy of the cervix and endometrium in a 28-year-old woman with abnormal uterine bleeding. The cervical biopsy demonstrated surface ulceration and underlying patchy necrosis of endocervical clefts and stroma. The endometrium was late secretory, with striking patchy necrosis of gland epithelium and stromal cells. Both sites contained occasional epithelial and stromal cells with nuclear inclusions consistent with HSV infection. Viral culture further confirmed the presence of HSV. Immunohistochemistry demonstrated the presence of HSV antigens in the tissue, and ultrastructural study of the endometrium revealed viral particles within epithelial and stromal cells. The results suggest endometrial involvement via an ascending infection from the cervix. Recognition of this unusual pattern of endometrial inflammation may facilitate diagnosis of additional cases.

Malignant mixed müllerian tumor of the uterus with neuroectodermal differentiation

A case of malignant mixed müllerian tumor of the uterus with neuroectodermal differentiation is reported. The most notable feature of the tumor was its large component of central nervous system tissue containing both glial and neuronal elements. The islands of neural tissue were admixed with more conventional carcinomatous and sarcomatous elements typically found in tumors of this type. The neuroectodermal component was conspicuous in the residual uterine tumor removed after radiotherapy, but not in the initial biopsy specimens. The patient died after developing local recurrence and distant metastases, which were treated with chemotherapy.

Endometrial biopsy in the cycle of conception: histologic and lectin histochemical evaluation

The histologic features and lectin binding patterns of endometrial tissue obtained in 16 cases of inadvertent biopsy during the cycle of conception were studied. Six biotinylated lectins that bind to specific glycoconjugates of secretory or gestational endometrium in paraffin-embedded tissue were used. These lectins were wheat germ agglutinin (WGA), Ricinus communis agglutinin-I (RCA-I), Concanavalin A agglutinin (Con-A), peanut agglutinin (PNA), Dolichos biflorus agglutinin (DBA), and soybean agglutinin (SBA). On review, the histologic sections showed day 20 to 26 patterns. In retrospective analysis, 15 of the 16 cases had increased stromal edema and vascular congestion compared with endometria of equivalent postovulatory dates not associated with conception. In 2 cases, spiral arterioles showed increased thickness. There was no evidence of renewal or prominence of glandular secretions. Most lectin binding was similar to that of the secretory phase of the menstrual cycle (WGA, RCA-I, gland lumenal secretions and stromal granulocytes; Con-A, gland cell cytoplasm and predecidua). There was focal, irregular staining of gland secretions with PNA, DBA, and SBA, lectins that generally react only with gland secretions in later gestation. These results indicate that vascular changes including edema and congestion appear to be the earliest persistent morphologic manifestations of the pregnant endometrium. Secretory gland changes, however, are subtle and are not identifiable by routine histology.

Trophoblastic tumors: ultrastructural comparison of choriocarcinoma and placental-site trophoblastic tumor

Ten trophoblastic tumors, including seven classical choriocarcinomas, two choriocarcinomas with atypical histology, and one placental-site trophoblastic tumor (PSTT), were studied to compare their fine structural features. Ultrastructurally, the classical choriocarcinomas showed well-defined cytotrophoblasts and syncytiotrophoblasts. The cytotrophoblasts were primitive epithelial cells, while the syncytiotrophoblasts were complex cells with multiple nuclei and dense cytoplasm containing dilated endoplasmic reticulum, lysosomes, vesicles, and tonofilaments. The syncytiotrophoblast cell membranes often contained numerous microvilli. In the choriocarcinomas, scattered intermediate trophoblasts showed features transitional between the cytotrophoblasts and the syncytiotrophoblasts, with moderately complex cytoplasm containing some of the organelles found in the syncytiotrophoblasts. Histologically, the atypical choriocarcinomas showed a predominance of mononucleate and binucleate cells and indistinct syncytiotrophoblasts. Ultrastructurally, these atypical tumors were composed largely of intermediate trophoblasts, yet contained scattered syncytiotrophoblasts with microvilli in compressed aggregates. The PSTT was composed primarily of intermediate trophoblasts that contained prominent paranuclear filaments not seen in the intermediate trophoblasts of the choriocarcinomas. Rare cells resembling syncytiotrophoblasts were found in the PSTT, but no cytotrophoblasts were observed. Immunoreactivity for human chorionic gonadotropin and human placental lactogen was found in the intermediate trophoblasts and syncytiotrophoblasts of both the choriocarcinomas and the PSTT, demonstrating functional homology between these tumors despite some ultrastructural differences. These results demonstrate ultrastructural features of trophoblastic cells that correlate with the morphologic diversity seen in these tumors by light microscopy. Furthermore, the comparisons suggest that the PSTT is composed of a distinct form of intermediate trophoblast that appears to reflect its origin from the extravillous trophoblast.

Analysis of multiple organ system failure in trauma and nontrauma patients

Multiple organ failure (MOF), a syndrome of recent evolution, has resulted from advancements in both surgical and trauma care. A prospective study of organ failure (OF) was conducted for 203 consecutive admissions to the surgical intensive care unit (SICU) between September 1986 and June 1987. Diagnosis, operations, age, OF, outcome, and culture data were recorded for each patient. OF definitions consistent with the literature were used to identify pulmonary, renal, hepatic, cardiovascular (CVS), gastrointestinal (GI), hematologic-coagulation, and central nervous system (CNS) failure. Eighty-two patients developed OF (40.4% incidence). The distribution of OF was 65 per cent trauma (T) and 35 per cent nontrauma (NT). Combined mortality for OF was 46 per cent (T = 34% and NT = 69%). The mortality of organ failure increased with the number of failed systems in the total population as well as in both T and NT groups. For the total population, the mortality by number of systems failed was no system, 1.3 per cent; one system, 13 per cent; two systems, 34.5 per cent; three systems, 75 per cent; four or more systems, 92.9 per cent. The incidence and mortality for each system is listed. Sepsis occurred in 62.1 per cent of NT patients (88.9% mortality) and in 30.2 per cent of T patients (31.3% mortality). Mortality was weakly associated with age in groups matched for severity of OF.

Prevention of postoperative pericardial adhesions with hydrophilic polymer solutions

Pericardial adhesions subject patients requiring cardiac reoperation to potential injuries of the heart, great vessels, and extracardiac grafts during resternotomy. We evaluated polyvinylpyrrolidone (PVP) and a methlycellulose derivative (MCD) as intraoperative irrigating solutions in the prevention of postoperative pericardial adhesions. Fifteen dogs weighing 15 to 20 kg were divided into three equal cohorts and subjected to left thoracotomy with pericardiotomy. Prior to surgical manipulation, the pericardial cavity was irrigated with either PVP, MCD, or Ringer's lactate (RL). Serosal injury stimulating intraoperative trauma was induced by gauze sponge abrasion of the epicardium and inner surface of the pericardium and by allowing desiccation of serosal surfaces for 30 min. The pericardial cavity was evaluated for adhesion formation 6 weeks postoperatively by reoperation. Two independent observers, unaware of the study solution, evaluated the extent and severity of pericardial adhesions on a 0-4 scale. All dogs in the RL control group had surgically significant adhesions and a mean adhesion score of 3.2 +/- 1.1. In contrast, no PVP- or MCD-treated dog had surgically significant adhesions. The mean adhesion scores were 0.2 +/- 0.4 for PVP and 0.5 +/- 0.7 for MCD. Our results indicate that PVP (P less than 0.004) and MCD (P less than 0.024) significantly reduce pericardial adhesion formation when compared to RL. Clinical application of PVP or MCD for the prevention of pericardial adhesions should reduce morbidity and mortality of cardiac reoperation.

Hospitalization in dialysis patients

During 1981, 946 patients with advanced renal failure who were maintained by dialysis were studied to assess the frequency and the duration of hospitalizations and to identify complications that prompted hospitalization. Five hundred fifty-eight patients (59%) were hospitalized for a total of 1,207 times (mean of 1.8 stays/yr and 15 days/yr at risk for the entire group). The major reasons for hospitalization were dialysis access problems (25%), gastrointestinal complications (13%), and cardiac complications (13%). Both the rate of stays/yr and the rate of days/yr increased with advancing age and were highest in patients who died during the year of study. Both the rate and the duration of hospitalization were higher for patients maintained by peritoneal dialysis than for those on hemodialysis (P less than 0.001). In patients younger than 45 years of age, diabetics had more frequent and more prolonged hospitalizations than nondiabetics, whereas in those 46 to 60 years of age, complications other than diabetes predisposed to hospitalization. In those 61 years of age or older, in whom hospitalization rates were the highest, no single risk factor could be identified as predisposing to hospitalization other than age and peritoneal dialysis. Although the interactions of these factors were not assessed, considerable agreement existed with previous studies that had been analyzed in a more sophisticated manner.

Long-term dialysis and renal transplantation in lymphatic leukemia

With increasing experience and skill with renal transplantation and dialysis, many disorders that were previously thought to contraindicate these procedures are no longer regarded as contraindications. We have previously reported that transplantation can successfully be performed in patients who have had malignant diseases if they seem to be cured after approximately 12 months. Although incurable malignancies have usually been regarded as absolute contraindications, successful dialysis and transplantation have been achieved in a patient with chronic lymphatic leukemia.